1. Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for configuring a reference signal.
2. Related Art
In the Long Term Evolution (LTE) release 12, intensive research is carried out on performance improvement in terms of a capacity, coverage, coordination between cells, and costs. In the LTE release 12, for such performance improvement, the introduction of various techniques, such as small cell enhancement, macro cell enhancement, a new carrier type, and machine type communication, are being discussed in a technical aspect.
The improvement of the capacity and coverage, that is, the target of the LTE release 12, may be achieved by small cell enhancement based on an inter-site carrier aggregation, integration between LTE-Wireless Local Area Networks (WLANs), and macro cell enhancement. As the size of a cell is reduced, the amount of traffic that is signaled when UE moves may be increased because the UE frequently moves between cells. In order to solve such a problem, a small cell may be optimized by reducing signaling transmitted from a Radio Access Network (RAN) to a core network using small cell enhancement.
A New Carrier Type (NCT) is a frame type that is newly defined differently from the configuration of a legacy frame. The NCT may be a carrier type optimized for a small cell, but may also be applied to a macro cell. In the NCT, overhead generated due to the transmission of a Cell-specific Reference Signal (CRS) can be reduced, and a downlink control channel can be demodulated based on a demodulation reference signal (DM-RS). By newly defining the NCT, the energy of a base station can be reduced and interference occurring in a heterogeneous network (HetNet) can be reduced. Furthermore, reference signal overhead occurring when data is transmitted using a plurality of downlink antennas can be reduced using the NCT. More specifically, the NCT maintains the existing frame structure (e.g., a CP length, a subframe structure, and duplex mode), but may be defined as a carrier that is not backward compatible to rel-11 and below UEs) and that is different in the structure of an actually transmitted reference signal.